Based on results from large ensemble simulations with the Community Earth System Model, we show that internal variability alone leads to a prediction uncertainty of about two decades, while scenario uncertainty between the strong (Representative Concentration Pathway (RCP) 8.5) and medium (RCP4.5) forcing scenarios [possible paths for greenhouse gas emissions] adds at least another 5 years. (dotearth.blogs.nytimes.com)
For scenario uncertainty (which the IPCC strategy arguably is, even though they don't seem to admit it), the strategy should be robustness: no regrets strategies that are win - win whether or not CO2 turns out to be a problem of the magnitude suggested by the IPCC. (judithcurry.com)
I have argued previously that the uncertainty surrounding future climates is best characterized by scenario uncertainty, in the sense of modal logic whereby individual model simulations should be regarded as a modal statement of possibility: (judithcurry.com)